1. Field of the Invention
The present disclosure generally relates to an image forming apparatus having a sheet conveying system and a waste toner tank, and more particularly to a moving system configured to be moved by a driving force transmitted via a sheet conveying system.
2. Discussion of the Background
As for an image forming apparatus such as a copying machine, a facsimile machine, a laser beam printer, it is necessary, for various reasons, to prevent sheet conveying rollers from being reversed.
For example, to correct a skew feed of a sheet, a leading edge of the sheet is abutted against a nip portion of a pair of registration rollers, and the sheet is conveyed for some distance by sheet conveying rollers disposed upstream of the registration rollers in a sheet conveying direction to form a loop of the sheet.
At this time, unless a reverse preventing mechanism for preventing the sheet conveying rollers from being reversed is provided, the sheet conveying rollers may be rotated in a reverse direction (i.e., in the direction opposite to the sheet conveying direction) due to a tension of the sheet.
As a result, the loop of the sheet disappears, resulting in an inferior sheet skew correction. At worst, the leading edge of the sheet retreats from the nip portion of the registration rollers toward the sheet conveying rollers so that a miss-feeding of the sheet occurs.
Generally, a sheet separation roller is disposed upstream of the sheet conveying rollers in the sheet conveying direction. The sheet separation roller rotates in a reverse direction to separate the uppermost sheet from the sheets fed out from a sheet feeding cassette.
The above-described inferior sheet skew correction and miss-feeding of sheets are typically caused when a force is exerted in a sheet returning-back direction.
To obviate the above-described drawbacks, a reverse preventing mechanism for preventing sheet conveying rollers from being reversed is provided in an apparatus that performs a sheet conveying operation.
FIGS. 1, 2A, and 2B illustrate a background reverse preventing mechanism for sheet conveying rollers used in an image forming apparatus.
A roller clutch (one-way clutch) 100 shown in FIG. 1 is generally used as a reverse preventing mechanism.
In the configuration of the roller clutch 100, each of a plurality of needle pins 120 is disposed in a hole-shaped clearance 140 (FIG. 2A) formed between the circumferential surface of a roller shaft 110 and an outer ring 160 such that the plurality of needle pins 120 contact the circumferential surface of the roller shaft 110.
As shown in FIG. 2B, the clearance 140 includes a narrow width portion B and a wide width portion C. Regularly, each of the needle pins 120 is biased by a spring 150 toward the narrow width portion B of the clearance 140. The size of an opening 140a of the clearance 140 is set such that the needle pin 120 can be prevented from falling through the clearance 140.
In this configuration of the roller clutch 100, when the roller shaft 110 is rotated in a direction indicated by arrow A in FIGS. 2A and 2B (i.e., a counter-clockwise direction), the needle pin 120 moves toward the narrow width portion B of the clearance 140 due to friction between the needle pin 120 and the roller shaft 110. By catching the needle pin 120 in the narrow width portion B of the clearance 140, the roller shaft 110 and the roller clutch 100 are locked as shown in FIG. 2B.
When the roller shaft 110 is rotated in a reverse direction (i.e., a clockwise direction), the needle pin 120 moves toward the wide width portion C of the clearance 140 by overcoming the biasing force of the spring 150, and thereby the roller shaft 110 rotates freely in the clockwise direction.
The outer ring 160 is disposed between the roller clutch 100 and a holder 130, and has a function of positioning the holder 130 relative to the roller clutch 100.
FIG. 3 is a schematic view of a sheet conveying roller mechanism provided with the background reverse preventing mechanism for use in an image forming apparatus.
As shown in FIG. 3, a plurality of sheet conveying rollers 3 are attached on a roller shaft 35 rotatably disposed between a first side plate 31 and a second side plate 32 via a first bearing 33 and a second bearing 34, respectively.
A plurality of driven rollers 37 attached on a driven shaft 36 contact the sheet conveying rollers 3 with a predetermined pressure, respectively, to convey a sheet without fail by applying a frictional force to the sheet at the nip portions between the sheet conveying rollers 3 and the driven rollers 37.
As shown in FIG. 3, the roller clutch 100 is often used as a bearing by pressing the roller clutch 100 into the second bearing 34 that supports one side of the roller shaft 35.
In an image forming apparatus, the sheet conveying rollers 3 and an image forming device are generally disposed between the pair of first side plate 31 and second side plate 32. A drive system such as gears, motors, and clutches is disposed at the outside of one of the first side plate 31 and second side plate 32. Such a drive system may be disposed on each side of the first side plate 31 and second side plate 32 instead of one side thereof.
However, because wires and gear trains used for a motor and reduction gears need a predetermined space to operate, if such a drive system is disposed on each side of the first side plate 31 and second side plate 32, the width of the apparatus increases. Therefore, the layout of a drive system concentrates on one side of the apparatus in order to save space.
In a recent space-saving printer or multi-function apparatus, the space for the layout of units is restricted, and therefore some units need to be disposed on a side opposite from a drive source relative to a sheet conveying area.
For example, a waste toner tank may be applied to this case. The waste toner tank is preferably disposed at the outside of one of the first side plate 31 and second side plate 32 for easy maintenance.
On the side where a drive system is provided, a motor, a structure for supporting the motor, and shafts for transmitting a drive force of the motor to each unit are disposed.
Further, a waste toner conveying path for conveying waste toner from an image forming device, which is disposed between the first side plate 31 and second side plate 32, to the waste toner tank needs to protrude through one of the first side plate 31 and second side plate 32. Therefore, it is difficult to dispose the drive system and the waste toner tank on the same side of one of the first side plate 31 and second side plate 32.
To drive a unit such as waste toner tank disposed on a side opposite from a first drive source such as motor, a second drive source needs to be provided on a side opposite from the first drive source.
Such an arrangement costs extra money for a motor, a driver, attaching parts, and electric wires. Further, measures against electromagnetic waves and noise generated from electric wires and motors need to be taken on both sides of the first side plate 31 and second side plate 32. Accordingly, the design for the above-described image forming apparatus is complicated.
Moreover, to enhance maintenance of a waste toner tank in an image forming apparatus, it is desirable that the waste toner tank is disposed at the outside of a side plate located on a side opposite from a drive system. This location of the waste toner tank is convenient for a user who replaces the waste toner tank when the waste toner tank is full.
Generally, for safety reasons, the maintenance of a drive system is conducted by a customer engineer. Further, a user replaces a photoconductive member/cleaning unit (PCU) and an intermediate transfer belt unit, for example, by opening a cover disposed on a side opposite from the drive system. It is preferable that the number of covers to be opened for maintenance is reduced to a minimum. Therefore, the same cover to be opened for maintenance is preferably shared among the waste toner tank, the PCU, and the intermediate transfer belt unit.
When the above-mentioned background art is applied to an image forming apparatus capable of color copying, a plurality of image forming devices (e.g., process cartridges) are provided in a slanted manner to save space in the image forming apparatus and to improve productivity of the image forming apparatus.
Therefore, the waste toner is piled at a position, which is lower than a toner ejection port of the image forming devices, in a waste toner tank, and a waste toner transporter (e.g., auger) is provided in a slanted manner for flattening a height of the piled waste toner in the waste toner tank. In such a case, the auger may be driven by a roller, for example. Such a roller may be a registration roller, a sheet conveying roller, a sheet feed roller, a sheet ejection roller, for example.
If a sheet ejection roller is used as a drive roller, a timing belt and a plurality of gears are required to drive the waste toner transporter (e.g., auger) because a distance between the sheet ejection roller and the waste toner transporter (e.g., auger) is long. Accordingly, the image forming apparatus unfavorably increases its required space and cost. In addition, a detachment of the process cartridges may be hindered in such a configuration.
As above-mentioned, toner ejected from the image forming devices (e.g., process cartridges) after image transfer is recovered in the waste toner tank. Such toner may be piled in a mountain shape when recovered in the waste toner tank.
Such toner may be piled in a shape having a plurality of mountains and valleys because an amount of recovered toner may vary for each color toner. Therefore, such mountains and valleys should be flattened by using a screw-shaped auger which moves toner from one place to another. If such a flattening operation is not conducted properly, some drawbacks may happen as discussed below.
In one case, a toner sensor may detect that the waste toner tank is full of waste toner even if some space still remains in the waste toner tank. In another case, waste toner may be piled at a toner ejection port and clog a waste toner pipe, thereby toner may not be ejected from the toner ejection port.
In the case of a color copying machine, the amount of waste toner of each color is different because the amount of toner to be used for image forming depends on the colors most often printed. Accordingly, the flattening operation of the waste toner for a color copying machine is more demanding than for a monochrome copying machine.
Although the amount of waste toner may depend on the types of toner used, process conditions, and environmental conditions, it is preferable to rotate a waste toner transporter (e.g., auger) as long as possible when an image forming operation is conducted.
In one case, a sheet feed roller or a sheet conveying roller may be used to transmit a driving force to the waste toner transporter (e.g., auger). However, if a sheet is fed from a sheet feed port without using such sheet feed roller or the sheet conveying roller, the waste toner transporter (e.g., auger) is not driven by the sheet feed roller.
If such a sheet feed port is used continuously to feed the transfer sheet, waste toner may clog the waste toner pipe because the waste toner transporter (e.g., auger) is not driven by the sheet feed roller or the sheet conveying roller.
In addition, if the sheet feed roller is activated to drive the waste toner transporter (e.g., auger) when the above-mentioned sheet feed port is used for sheet feeding, another transfer sheet is also fed from the sheet feed roller. If another transfer sheet is fed in addition to the transfer sheet fed from the above-mentioned sheet feed port, an image forming apparatus may cause a drawback on image forming operation.
Hereinafter a case using a sheet conveying roller to drive the waste toner transporter (e.g., auger) is briefly explained.
When the sheet conveying roller transports transfer sheets, the sheet conveying roller drives the waste toner transporter (e.g., auger), thereby a flattening operation of the piled toner can be conducted properly.
However, when one image forming operation or a continuous image forming operation is conducted without transporting a transfer sheet, the waste toner transporter (e.g., auger) is not driven by the sheet conveying roller even though toner is recovered in the waste toner tank. Thus, the waste toner is not flattened in the waste toner tank, and clogging of waste toner pipe may occur, or a toner sensor may detect an untimely (i.e., premature) “toner-full” condition in the waste toner tank.
The above-mentioned image forming operation without transporting the transfer sheet includes “image concentration adjustment” and “color displacement adjustment,” for example.
In case of the “image concentration adjustment,” a predetermined image pattern is formed on a photoconductive member, and transferred to an intermediate transfer belt. Then an image concentration sensor reads concentration information of the image. Based on such information, image forming conditions can be automatically adjusted.
In case of the “color displacement adjustment,” color displacement of four color images superimposed on the intermediate transfer belt from the four process cartridges is corrected.
Such correction is conducted when power is supplied to an image forming apparatus or during continuous printing, for example. As similar to the “image concentration adjustment,” a predetermined image pattern is formed on a photoconductive member, and transferred to an intermediate transfer belt. Then a sensor reads image information. Based on such information, image forming conditions such as traveling speed of the intermediate transfer belt, timing and position of optical writing are corrected.